This paper aims to investigate the effect of the water-to-cement ratio on the passive layer forms of steel in cement paste.
Three sets of paste samples, each set containing three samples with a steel bar embedded in the center, were prepared using different W/C ratios of 0.35, 0.45 and 0.6, respectively. Electrochemical experiments, including Electrochemical impedance spectroscopy, linear polarization resistance and Mott-Schottky, were used to study the passive layer.
Results showed that increasing the water-to-cement ratio reduced corrosion current densities and shifted the corrosion potential to more positive values. Nonetheless, the passive layers formed in a lower water-to-cement ratio had fewer defects, suggesting higher stability. The thickness of the passive layer was inversely correlated with the water-to-cement ratio. It was hypothesized that the variations in the kinetics of oxygen reduction and the high alkalinity maintained at lower water-to-cement ratios were the reasons for such observations.
This paper for the first time, investigated the effect of water-to-cement ratio on passive layer.
